= Solution
The hemispherical component needs 100.0 eV <electrons>, whereas <electrons> arrive at its entrance optics with 111.4 eV. The optics must therefore remove \b[11.4 eV], requiring a \b[retarding-potential magnitude of 11.4 V]. For a negative <electron>, moving to a more negative electrostatic potential increases potential energy, so the retarding region is 11.4 V negative relative to the analyser entrance. Equivalently the hemisphere entrance is 11.8 V negative relative to the sample vacuum reference after including the 0.4 V contact step. Reporting 11.8 V as the additional instrument retardation would count the contact correction twice.
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